If you are having excruciating pain down your buttock and leg, you are suffering from wa is known as cyatica (sp) - you have a trapped nerve and no amount of core, bio, or chyro is going to fix it I'm afraid. I had the same problem with a broken disc between L5/S1 - had to have 2 back ops (microdisectomy and laminectomy) - busy with extensive physio & bio rehab now, and only able to start light on-road cycling recently. You need to see a neurosurgeon and probably have a MRI to determine whether to operate or not. Sorry fr the bad news, but trust me - I've just been there!